The invention relates to an extruding device which includes an extrusion head for connection to at least two extruders, as well as at least one tool for shaping a product composed of at least two extruded materials.
Devices of this type are used in particular for producing strip shaped elements of elastomer materials for the manufacture of tires. Such strips frequently consist of two or more layers of different elastomer materials. These layers frequently have a poor electrical conductivity. The use of automobile tires which are constructed from such continuously poorly conducting layers leads to the risk of an electrostatic charging of the vehicle.
For avoiding this effect of the electrostatic charging, it is already known to embed additional electrically conductive areas in the strip shaped materials. For example, EP 1 103 391 describes a device for co-extruding rubber mixtures which is arranged in the area of the extrusion head near the discharge opening of a pipe-like nozzle which divides the oncoming material into two partial flows. On the side of the nozzle facing away from the flow direction, a discharge gap is located from which the additional material emerges which then reconnects the two areas which had previously been separated. The additional material forms the layer which penetrates the electrically nonconductive layers.
By placing such an additional nozzle in the principal flow path, the flow conditions, particularly the occurring flow resistances, are changed. Therefore, it is difficult to achieve an exactly reproducible material distribution when using such a device.